Linux basic command: Install and Configure Remote Access To Your Ubuntu Desktop

This guide explains how you can enable a remote desktop on an Ubuntu desktop so that you can access and control it remotely. This makes sense for example if you have customers that are not very tech-savvy. If they have a problem, you can log in to their desktops without the need to drive to their location. I will also show how to access the remote Ubuntu desktop from a Windows XP client and an Ubuntu client.
I do not issue any guarantee that this will work for you!

1 Preliminary Note

I have tested this on an Ubuntu 7.10 (Gutsy Gibbon) desktop.

2 Enabling The Remote Desktop

We don't have to install anything to enable the remote desktop on Ubuntu. All we have to do is go to System > Preferences > Remote Desktop:

In the Remote Desktop Preferences window, you can configure the remote desktop connection. If you want others to just see your desktop, but not be able to make changes, enable Allow other users to view your desktop only. If they should be able to change settings (e.g. repair your system if there are problems), enable Allow other users to control your desktop as well. Then you should write down the command that you can use on other Linux clients to connect to your desktop; in my case it's:

vncviewer falko-desktop:0

Then there are the security settings. If someone connects to your desktop and you want to be able to block or allow that connection, enable Ask you for confirmation. This makes sense only if someone is actually sitting in front of the system. If you want to connect to your office desktop or any other sysem that only you have access to, then don't enable this option.
But what you should do is set a password for your remote desktop (without a password anyone who happens to find out your system's address - e.g. by scanning the network - can access your desktop):

That's it - the remote desktop can now be used!
You've noticed that the command to connect to the desktop contains the computer name and not the IP address (vncviewer falko-desktop:0). To avoid problems when the computer name (falko-desktop) cannot be resolved in the network, it's a good idea to find out the system's IP address and use that one instead in the vncviewer command. Right-click on the network icon (the two monitors) in the upper right corner and select Connection Information:

A window with details about your current network configuration opens. In it you can find your IP address (192.168.0.217 in my case) - write it down somewhere:

Instead of

vncviewer falko-desktop:0

we can now use

vncviewer 192.168.0.217:0

as well to connect to the remote desktop.
If you want to connect to your desktop from outside your network, you must use your router's public IP address (or get yourself a free hostname from dyndns.org pointing to your router's public IP address). Port 5900 (which is used by the remote desktop) must be open in the firewall, and your router must forward port 5900 to the Ubuntu desktop.

3 Connecting From A Windows XP Client

In order to connect from a Windows XP system, we must install a VNC client on the Windows system. There are multiple free VNC clients available, e.g. from http://www.realvnc.com/products/download.html. Select the Free Edition...

... and click your way through the following pages. On the download page, select the VNC Free Edition Viewer for Windows executable...

... and save it on the system, e.g. the desktop. The VNC Free Edition Viewer for Windows is a standalone executable, i.e., you don't have to install it to use it. After the download has finished, simply double-click the file...

... and the VNC Viewer starts. Type in the remote desktop's IP address (you can either type 192.168.0.217:0...

... or just 192.168.0.217)...

... and the password for the remote desktop (leave the Username field empty), then click on OK:

If all goes well, you should now see the remote Ubuntu desktop in a new window:

4 Connecting From An Ubuntu Client

On an Ubuntu client, we don't have to install any software to connect to the remote desktop - it's all there. We can simply use the vncviewer command from chapter two. Open a terminal (Applications > Accessories > Terminal):